6 Journal of Comparative Neurology. • 



seem that popular language has crystallized an opinion that in 

 one case the process is passive and in the other active. We are 

 slow to reject the calm and impartial dicta of common sense 

 — in fact, in some sense, this dictum is likely to be found cor- 

 rect, though the meaning of active and passive in such connec- 

 tions may suffer a good deal as the result of analysis. 



External Attention. — One of the first evidences of awaken- 

 ing psychical life in the child is seen in the motions of the eye- 

 balls as he attempts to follow moving objects, and one of the 

 last evidences that is given that the departing spirit still hovers 

 over the threshold is the same seeking motion of the eyes. As 

 the most direct and unbiased avenue to consciousness, vision is 

 the best sense from which to study the phenomena of external 

 attention. Now if the eye be fixed upon a given field of view 

 coinciding with the visual field of the retina it is evident that all 

 parts of the field are capable of producing an impression on the 

 retina and so on the nerve fibres and brain; in fact, each such 

 spot does stimulate a point in the brain corresponding to the 

 spot in the retina on which it falls. This neural irritation is not 

 yet in consciousness but is a part of the "content of sense," 

 or sensory material for consciousness. Returning to the retina, 

 if the field of view be uniform and uniformly illuminated and 

 the gaze be fixed upon it under circumstances excluding other 

 visual distractions a small disc will appear in the centre of 

 the field of view which is somewhat more bright than the sur- 

 rounding portions.* 



This little experiment is the physiological aspect of the 

 fact that there is in the axial pole of the retina a spot in which 

 only the cones are present and consequently the intensities of 

 light and shade are more vivid than elsewhere in the retina. 

 This relation would lose most of its significance were it not for 

 another relation connected with it. 



^The descriptions of most of the experiments accompanying the lecture are 

 omitted as they are of such a nature as will readily suggest themselves to the 

 experienced reader. 



